Barao stopped Faber with a first-round TKO as Faber covered up on the ground. But at the stoppage, Faber immediately looked to referee Herb Dean wondering why he didn't heed the thumbs-up signal he tried to give. The end came at the 3:42 mark of the fight.

The bantamweight title bout was the main event of the UFC 169 pay-per-view at Prudential Center in Newark, N.J.

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But Faber survived, got back to his feet and kept swinging. So, too, did Barao. Barao stunned Faber again moments later, but again the challenger survived – only to get dropped again seconds later.

As Faber covered up, Barao landed punches to the side of Faber's head. Faber didn't answer – but appeared to be blocking most of the strikes. When referee Herb Dean moved in to stop the fight, Faber immediately protested. Replays appeared to show Faber trying to give thumbs up that he was OK taking the punches.

"It's very frustrating. I'm one of the most durable guys in the world," Faber said. "You get caught with punches. He told me to do something, so I gave him a thumbs up right before he stopped it. Herb's a great referee ... but I had some more fight in me.

"I don't want to take anything away from Barao. He caught me with a clean punch. But I wasn't out, and I'll be back."

Barao said he knew he was in for a hard fight in the rematch with Faber, even though the challenger took the fight on just a month's notice, filling in for Dominick Cruz.

"I fought Urijah before. He's a very tough guy, and I knew he was going to be a tough fight," Barao said. "I hit him with that right hand. I saw he was groggy, I saw that I rocked him, and I just stayed on him."

Barao (32-1 mixed martial arts, 7-0 UFC) continued one of the greatest unbeaten streaks in MMA history, extending his run to 33 straight without a loss. Faber (30-7, 6-3) had a four-fight win streak snapped with the loss and now has dropped six straight title fights.